1. Field of the Invention
This invention relates to a tubular incandescent lamp, and more particularly to a long tubular incandescent lamp for use in electronic copying machines which has incorporated therein a filament having non-light-emitting parts.
2. Description of the Prior Art
Many studies and inventions have been made on a long, tubular incandescent lamp for use in electronic copying machines which has incorporated therein a filament having light emitting and non-light-emitting segments.
Recent trends in electronic copying machines employing a lamp of this kind is to speed up operation and reduce power dissipation. To meet these objectives, a very high degree of performance is now required for the lamp used in such copying machines.
For example, to speed up the machine operation, the lamp scanning speed must be increased. In doing so, it is necessary to enhance the shock resistance of the lamp, while appropriately reducing the filament weight and adopting the right structure for the lamp.
To reduce machine power dissipation, the lamp is designed to decrease its power consumption by using a sensitizer of high sensitivity. In doing so, changes in the distribution and quantity of light of the lamp are liable to affect the copying operation; consequently, it is necessary to control the distribution of light with high precision and to reduce the error in changes in the quantity of light.
To fulfill such requirements imposed on the tubular incandescent lamp for use in the electronic copying machine, studies are now being done to obtain an optimum design of the lamp.
Conventional tubular incandescent lamps are roughly divided into the following types:
(a) A segment type in which light emitting and non-light-emitting segments are connected alternately with each other (U.S. Pat. No. 3,416,024).
(b) A short bar type in which continuous coil filament is short-circuited by short bars at a predetermined position (Japanese Utility Model Publication Gazette No. 359/70).
(c) A skipped winding type in which a continuous coil filament is made roughly-pitched at predetermined positions to provide portions which are inhibited to light (U.S. Pat. No. 3,295,007).
(d) A comprise type of the abovesaid types (a) to (c). All these conventional lamps have both merits and demerits, and studies for improvement are being made to keep abreast of developments in the present electronic copying machine art.